The interaction of track, freight
vehicles and their loads
The RAIB perspective
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Outline
Controlling the risk of derailment
Analysis of RAIB investigation findings
Areas of recommendation
Key issues arising
Case studies
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Controlling the risk of derailment
1 Track
Geometric limits, and specific construction
requirements defined in:
TSI Infrastructure; and/or
Railway Group Standard GC/RT5021
Network Rail construction and maintenance
standards
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Controlling the risk of derailment
2 Rolling stock
Requirements for resistance to derailment defined
in:
TSI Wagons (EN 14363, ‘Testing for the acceptance of
running characteristics of railway vehicles’)
Railway Group Standard GM/RT2141
Rolling stock maintenance standards (usually
company specific)
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Controlling the risk of derailment
3 Loads conveyed by wagons
Laws and standards governing the loading of
wagons and containers
Standards, guidance, good practice and contractual
requirements governing the even distribution of loads within
containers/wagons, and the protection against loads shifting
Legislation for loading and packing of containers; eg
Merchant Shipping (Carriage of Cargoes) Regulations 1999
(no equivalent for rail)
Standards governing the distribution of weight on loaded
trains
o Longitudinal distribution (front to back)
o Lateral distribution (side to side)
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Controlling the risk of derailment
- container loading standards
IMO/ILO/UNECE guidelines for packing of cargo transport units
ISO 3874, ‘Series 1 freight containers – Handling and securing’
BS 5073, ‘British Standard guide to stowage of goods in freight
containers’
‘European best practice guidelines on cargo securing for road transport’
‘Code of practice – safety of loads on vehicles’
‘Safe transport of containers by sea – industry guidance for shippers and
container stuffers’
‘Working with containers – an Freight Transport Association best practice
guide’
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Derailment mitigation measures that are not
formally managed
Rail lubrication: reduces flange climb risk, but fitted to
reduce rail side wear
Wheel flange lubrication: reduces flange climb risk, but not
generally specified
Naturally occurring moisture and rail head contaminents
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The residual risk at the Vehicle/Track (V/T)
system interface
This is the V/T system interface risk that remains even when
track, train and loading are compliant with mandated
requirements:
Research work in the 1970s by the ORE B55 committee, which
underpins some of the current derailment standards,
acknowledged that ensuring (absolute) derailment safety would
mean ‘unjustifiably high costs of (vehicle) construction’. It
therefore proposed reducing the ‘stringency of conditions’ for
vehicles by finding a ‘compromise solution’
It is often argued that the risk of derailment remains acceptable
while allowing for the residual V/T system interface risk – the
RAIB understands that this is an argument based on the belief
that risk has already been reduced SFAIRP
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Do current track and rolling stock standards
cover all derailment risk at their interfaces?
Residual risk at the VTI
Principal causes of freight train derailments identified in
RAIB investigations 2005 to present
SF-4.1.8.1 v2 13.11.09
Condition of rolling stock, 5
Driver error, 3
Earthworks failure, 4
Overspeeding, 1
Interaction of uneven wagon loading and poor
track condition, 5
Interaction of deficient rolling stock and poor
track condition, 8
S&C condition, 2
Signaller error, 2
Track condition, 4
Train preparation, 3
Total = 38
Factors linked to V/T system interface
SF-4.1.8.1 v2 13.11.09 Interaction of
uneven wagon loading and poor track condition, 5
Interaction of deficient rolling stock and poor
track condition, 8
Total = 13 Of these, in 11 cases the track condition was permitted, albeit for a limited period of time (as shown below) Undefined = 2 30 days = 1 case 7 days = 2 cases 14 days = 4 cases 36 hours = 2 cases
Factors linked to V/T system interface
SF-4.1.8.1 v2 13.11.09
In cases where both track and train/load have
featured as factors, the following issues were found:
• Undetected or uncorrected twist (8)
• Cyclic top (2)
• Absence of check rail (2)
• Stiff bogie rotation (1)
• Frame/bogie twist (3)
• Defective suspension components (3)
• Poor ride performance when partially loaded (2)
• Weight distribution of the wagon’s load - lateral
asymmetry exacerbated by the longitudinal
asymmetry (5)
Factors linked to V/T system interface
SF-4.1.8.1 v2 13.11.09
Of these, three are of particular interest to the RAIB:
• Undetected or uncorrected track twist
• Cyclic top
• Absence of check rail
• Stiff bogie rotation
• Frame/bogie twist
• Defective suspension components
• Poor ride performance when partially loaded
• Weight distribution of the wagon’s load - lateral
asymmetry exacerbated by the longitudinal asymmetry
Some key issues
SF-4.1.8.1 v2 13.11.09
Undetected or uncorrected track twist
• How to better manage twist faults on the network,
particularly those at high risk locations?
• Can we be smarter in the way we measure and
evaluate the likely impact of track twist; is the 3m
base sufficient?
• Monitoring of track twist at locations where track
measurement trains do not run
Some key issues
SF-4.1.8.1 v2 13.11.09
Frame/bogie twist
• How prevalent is frame twist in existing fleets of wagons
and do we understand the associated risk posed by twisted
wagon frames?
• How do wagons with high torsional stiffness respond to
‘long-wave’ twist?
• How prevalent is uneven loading across bogies (and/or
incorrect packing) and is this allowed for in our current
understanding of derailment risk?
Use of track side equipment (eg GOTCHA)
• Can we use such equipment to identify individual wagons
with uneven wheel loads due to defects such as:
abnormal levels of frame twist?
excessive bogie twist or suspension defects?
Some key issues
SF-4.1.8.1 v2 13.11.09
Weight distribution of the wagon’s load - lateral
asymmetry exacerbated by the longitudinal asymmetry
• Do we understand the risk?
• Are there reasonable practicable measures that
can be taken: to prevent uneven (and insecure) loading at source eg
with shippers?
to detect dangerous levels of load asymmetry and
prevent it entering the railway network?
• Can we reduce the potential impact of lateral
asymmetry by controlling the extent of longitudinal
asymmetry?
Factors affecting wheel unloading
Recommendation 2 of report into the derailment at Camden
Road encourages industry to see this as a system issue.
Recommendation (summarised) is:
Freightliner and Network Rail should jointly:
research the factors that may increase the probability of derailment
when container wagons are asymmetrically loaded, including:
• sensitivity to combinations of longitudinal and lateral offsets in
loads that can reasonably be encountered in service;
• the effect of multiple track twist faults over various distances
and work with other industry stakeholders to identify, evaluate and
promote adoption of any additional reasonably practicable mitigations
capable of reducing the risk from asymmetric loading of wagons. 17
*at-risk wheel
Effect of offset payload on derailment risk
Typical effect Level track Twisted track
Q1 (kN) Q2 (kN) Qave (kN) DQ/Q Q1 (kN) Q2 (kN) Qave (kN) DQ/Q
No load offset 50 50 50 0% 35 65 50 30%
Longitudinal offset load 35 35 35 0% 20 50 35 43%
Lateral offset load 35 65 50 30% 20 80 50 60%
Lateral + Longitudinal load offset 20 50 35 43% 5 65 35 86%
Q1*
Q2
Increased longitudinal payload
offset increases the derailment
risk due lateral wheel load
imbalance DQ/Q = (Qave-Q1)/Qave
where: Qave = (Q1+Q2)/2
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Why re-examine this issue now?
The work of the RAIB shows that uneven loading of
wagons continues to be a major factor in the cause of
derailments
It is possible likely that the ‘historic norm’ will be influenced
by a number of changes significant changes; eg
Growth in the numbers of 40’ containers
Increase in max. weight of 20’ containers since 1994
Introduction of higher containers
Changes to the ways that containers are allocated to
wagons
Torsionally stiffer underframes may be making modern
container wagons more prone to long-base track twists
• The uneven and insecure loading of
containers is an issue that is bigger than the
rail freight sector. Is there any scope for pan-
freight learning and problem solving?
Extent of the issue
Other areas of recommendation relating to
the V/T system interface
More effective detection and management of track geometry
(various) ONGOING
Extended use of WHEELCHEX/GOTCHA to detect uneven
wheel loads due to wagon condition (KEB and Ely) ONGOING
Assessing the risk associated with uneven loading of bulk
materials (Santon) NOT FULLY ADDRESSED
Assessment of how changes to infrastructure or maintenance
arrangements can impact on the risk of derailment on tight
radius curves (Ordsall) ONGOING
Standard for assessing a wagon’s response to cyclic top
(Gloucester) ONGOING
Actions to address pedestal suspension lock-up (Ely and
Bordesley) ONGOING
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